Method and calculator unit for determining total damage to at least one rotating component of a drive train

ABSTRACT

A method for determining total damage to at least one rotating component of a drive train in a system, in particular a wind or wave energy system, includes determining over time during operation of the system a variable characterizing a rotational speed of the component and a variable characterizing a torque transmitted by the component. A load collective is determined in a calculator unit from the temporal progression of the variables, and the total damage is determined from a comparison of the determined load collective and a reference load collective.

The present invention relates to a method for determining theoretical total damage to at least one rotating component of a drive train and to a calculator unit for carrying out said method.

PRIOR ART

Even though the present invention is described primarily with reference to wind turbine generator systems (WTGS), it is not restricted to these but can in principle be used for all types of power generating plants and systems in which a drive train is designed with a view to the likely load collective. However, the invention yields particular advantages for systems in which making a replacement is a particularly complex operation, for example in the case of offshore systems.

Components having drive trains, such as for example gear mechanisms, couplings and connecting elements (shafts), are important component parts of various electrical energy generating systems, such as for example wind turbine generator systems, hydroelectric generator systems, etc. The drive train performs the task of establishing a mechanical connection between a drive input (for example a rotor of a wind turbine generator system) and a drive output (for example a corresponding generator), by way of which energy is transmitted by a rotational movement. Drive train components, such as gear mechanisms, serve the purpose of converting the rotational speed and the torque that occur at the drive input into values that correspond to the operating range of the generator. Shafts establish the mechanical connection between the components involved. Further components, such as mechanical brakes or the like, may also be integrated in the drive train. Couplings may be arranged if need be between two components, for example to compensate for misalignment.

Drive trains or the components thereof have a certain lifetime, which depends substantially on the loading (torque, torsion, vibrations, etc.). Drive trains can therefore be designed with a view to a likely (pre-calculated) load collective.

An essential precondition for the cost-effectiveness of wind turbine generator systems is that they are operated as far as possible without any interruptions. Unplanned operational interruptions in particular generate considerable repair costs, and often lead to insurance claims.

To avoid such disadvantages, WTGS are often provided with what is known as condition-oriented maintenance, which is for example performed on the basis of a vibration-based condition monitoring (CM) of rotor blades in corresponding condition monitoring devices or systems (CMS). Such measures allow for example the early detection of incipient damage in rotor blades. CMS are often designed for remote diagnosis, the condition messages being evaluated at certified diagnosis centers, often by specially trained personnel.

However, components for which there are no known monitoring possibilities are also used in WTGS, the invention being aimed at the drive train and the components thereof. As mentioned, these may be designed on the basis of the likely load conditions. However, the actual lifetime is not known during operation, and so servicing is not performed in a condition-oriented manner. There is therefore the need for the possibility of determining the lifetime of components of a drive train in energy generating systems while they are operating (“online”).

DISCLOSURE OF THE INVENTION

The invention proposes a method for determining total damage to at least one rotating component of a drive train, in particular of a wind turbine generator system or wave energy generating system with the features of patent claim 1 and a correspondingly designed calculator unit for carrying it out. Advantageous refinements are the subject of the subclaims and the description that follows.

ADVANTAGES OF THE INVENTION

The invention provides the possibility of determining total damage to at least one rotating component of a drive train, in particular in wind turbine generator systems or wave energy generating systems, while they are operating and making it available to condition-oriented servicing. For this purpose, the invention makes use in particular of detection of the torque transmitted by the component to be monitored and the rotational speed, in order to carry out a classification in the direction of the load collective. The detection of the actual collective of the load in practice and comparison with the design collective allow the total damage that has occurred thus far (corresponding to a degree of wear) of the component to be determined.

Preferred methods for determining the actual collective make use in particular of methods that are known from the area of structural durability. Particularly suitable are counting methods, peak-value, instantaneous-value and dwell-time methods or a rainflow classification.

Preferably, only a variable characterizing the torque over time is determined. The variable characterizing the rotational speed can be determined from the progression of the torque signal. For example in the case of a wind turbine generator system, the tower shadow results in a periodic irregularity in the signal. Periodic elements may possibly also be identified in speed signals of other systems.

The invention is suitable in particular for use in wind turbine generator systems and wave energy generating systems (flow and tidal power generating systems in the area of river and ocean energy utilization), since, as mentioned, servicing is particularly complex here. Since the loads acting on the system at a given instant are also extremely variable (as a result of greatly varying wind speed or flow), knowledge of the total damage is particularly advantageous.

A calculator unit according to the invention, for example as a component part of a monitoring device (CMS), is designed, in particular in terms of programming, for carrying out a method according to the invention.

Implementation of the invention in the form of software is also advantageous, since this makes particularly low costs possible, in particular if an implementing calculator unit is also used for other tasks, and is therefore present in any case. Suitable data carriers for providing the computer program are, in particular, floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs, and so on. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

Further advantages and refinements of the invention emerge from the description and the accompanying drawing.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the respectively specified combination but also in other combinations or on their own without reporting from the scope of the present invention.

The invention is schematically represented in the drawing on the basis of exemplary embodiments and is described in detail below with reference to the drawing.

DESCRIPTION OF FIGURES

FIG. 1 shows an energy generating system according to a particularly preferred embodiment of the invention.

FIG. 2 shows a torque progression, given by way of example, in a component to be monitored, for example the gear mechanism from FIG. 1.

DETAILED DESCRIPTION OF THE DRAWING

FIG. 1 shows in a schematic view the basic structure of an energy generating system 100, which is designed for carrying out the invention. The energy generating system 100 is formed as a wind turbine generator system with a rotor 1 and an electric generator 6, which are mechanically connected to one another by a drive train having a rotor drive-output shaft 2, a gear mechanism 3, a coupling 4 and a generator drive-input shaft 5. The rotor 1 is fitted as a drive input at an input end 1′ of the drive train 2-5, the generator 6 is fitted as a drive output at an output end 6′. Two rotary angle sensors 7, 8 on the rotor side 1′ and the generator side 6′ of the gear mechanism 3 each determine an angle φ₁ and φ₂, respectively, as variables characterizing the torque. The difference in angle corresponds to a torsion angle over the gear mechanism 3, which is proportional to a torsional moment, and consequently a torque.

A preferred torque detection may also make use of one or more strain gages, which are fitted on a shaft and the signal of which is proportional to the twisting of the shaft (torsion). A torsion measurement may also be performed by means of a magnetic field passing through the shaft or from a distortion of the same.

The measured values are transmitted to a calculator unit 9, which is designed in terms of programming for carrying out a method according to the invention. Total damage of the gear mechanism is calculated in the calculator unit 9 on the basis of the sensor signals.

The calculator unit is designed to detect the measuring signals over time. In particular in the case of wind turbine generator systems, the tower shadow results in an irregularity of the signal, from which the current speed of the rotor or the shaft 2 can be determined. This advantageously allows the torque and at the same time the speed to be determined by detecting just a signal characterizing the torque. The difference between the rotary angles φ₁ and φ₂ gives the torsion angle over the gear mechanism 3, which is proportional to the torsional moment, and consequently the torque.

A temporal progression of the torque determined is plotted in FIG. 2. A regular torque fluctuation caused by the tower shadow can be determined from the progression. The time period corresponds to the angle between two rotor blades, in the case of conventional systems 120°. The speed can be determined from the time period.

The time period, the speed and the measured variable that is proportional to the torque are classified in the calculator unit to form a load collective and are continuously summated. This produces a load collective that is applicable over the lifetime of the drive train of the wind turbine generator system and can be compared with the load collective originally taken as a basis for the core components of the system.

Taking into consideration various Wöhler curve exponents (for example for rolling bearings, toothings, etc.), something known as a degree of total damage can be determined and compared with a permissible target damage. From this comparison, a remaining lifetime estimate can be made for the core components of a WTGS, and this can be used inter alia for preventive maintenance and possibly the replacement of certain components. 

1. A method for determining total damage to at least one rotating component of a drive train of a system, comprising: determining a variable characterizing a rotational speed of the component over time during operation of the system; determining a variable characterizing a torque transmitted by the component over time during operation of the system; determining a load collective in a calculator unit from the temporal progression of the variables; and determining the total damage from a comparison of the determined load collective and a reference load collective.
 2. The method as claimed in claim 1, wherein determining the total damage includes determining the total damage to at least one component of a gear mechanism.
 3. The method as claimed in claim 1, wherein the reference load collective is a load collective for which the component has been configured.
 4. The method as claimed in claim 3, wherein the load collective for which the component has been configured takes into consideration the associated Wöhler curve exponent that characterizes the underlying damage mechanism.
 5. The method as claimed in claim 1, wherein the variable characterizing the torque transmitted by the component is detected and the variable characterizing the rotational speed of the component is determined from it in the calculator unit.
 6. The method as claimed in claim 5, wherein the determination of the variable characterizing the rotational speed of the component takes place on the basis of a point of significance in the temporal progression of the variable characterizing the torque transmitted by the component.
 7. The method as claimed in claim 1, wherein a rotary angle sensor upstream of the component and a rotary angle sensor downstream of the component are configured for determining the variable characterizing the torque transmitted by the component, and the torque transmitted by the component is determined from the difference between the two sensor values.
 8. A calculator unit configured to implement a method for determining total damage to at least one rotating component of a drive train of a system, the method including: determining a variable characterizing a rotational speed of the component over time during operation of the system; determining a variable characterizing a torque transmitted by the component over time during operation of the system; determining a load collective in a calculator unit from the temporal progression of the variables; and determining the total damage from a comparison of the determined load collective and a reference load collective.
 9. A system, comprising: a drive train train; a drive input fitted at an input end of the drive train; a drive output driven by the drive train and fitted at an output end of the drive train; and a calculator unit configured to implement a method for determining total damage to at least one rotating component of the drive train, the method including: determining a variable characterizing a rotational speed of the component over time during operation of the system; determining a variable characterizing a torque transmitted by the component over time during operation of the system; determining a load collective in the calculator unit from the temporal progression of the variables; and determining the total damage from a comparison of the determined load collective and a reference load collective.
 10. The system as claimed in claim 9, further comprising at least one torque sensor or at least two rotary angle sensors.
 11. The method as claimed in claim 1, wherein the system is configured as a wind turbine generator system or a wave energy generating system.
 12. The system as claimed in claim 9, wherein the system is configured as an energy generating system. 